I find the scenario believable, but I think the mechanism by which the 'good' politician is getting sacked is more complex. I think s/he is getting sacked because s/he spent a lot of political capitol on a difficult undertaking that doesn't bring much credit back to her/him. Improving decaying infrastructure doesn't insert a positive 'this politician accomplished' association into many voters minds. S/he's just doing the things that voters assume happen on their own anyway. On the other hand, the 'bad' politician that ignored the issue had a nice extra bit of political capitol to spend on flashier issues like crime, lowering taxes, etc.

So, rather than it being a "the people have spoken" situation, I think that the situation is driven by constraints on public attention for political issues. I don't think you would get many voters endorsing continued poisoning of the population when a marginal increase (or reshifting) of taxes could address the issue. Rather I think that it is rarely ever politically advantageous to spearhead these kind of issues (that is until it explodes into an attention grabbing crisis, as is now the case with Flint lead poisoning).

We can see this sort of thing in microcosm in office politics as well. How often are we complaining about always being reactionary and putting out fires instead of proactively taking care of problems before they can cause a lot of damage? Well, once a fire starts, everyone is keen to figure out what's causing it and how to deal with it. But recognizing the pre-conditions that could potentially lead to a fire, and then eliminating them sound much more boring[1], and often requires a concerted information campaign just to get people invested in supporting the mitigation. But if there's an actual [2] fire, people are immediately interested by the inherent drama of the situation, and attention is no longer a barrier to overcome.

[1] even that description of it sounded much more boring than the bit about fire! [2] an 'actual' figurative 'fire'. I know the wording is sub-optimal, but I'm pot committed to this metaphor so...